The present invention relates to a method for operating a transport system for printed products composed of printed sheets or signature.
The European patent document EP 1 334 938 A1 discloses a device for producing bound printed products. To produce these products, individual printed sheets are supplied to a continuously operating folding device and are folded therein. The folded sheets or signatures are then gathered in a gathering device to form a pre-product and are transferred to a transport device. The gathering device is provided with a sword, essentially extending parallel to the transporting direction of the transport device, on which respectively a predetermined number of signatures are gathered to form a pre-product.
The European patent document EP 1 270 479 A1 discloses a method for producing a print item which is composed of several printed products, gathered while positioned straddling. The printed products used to form a printed item are collected in a predetermined sequence along a joint path and are then stitched together. An intermittently circulating support surface is provided, which is supplied by a feeding device with printed products that are positioned straddling.
In the known prior art, the folded signatures must be gathered in a gathering device and must then be transferred to a transport device. Further, the signatures which are processed while moving through a continuously operating folding device in which the sheets are provided with a fold pointing in the movement direction of the conveying path, must be processed as individual sheets or signatures for the purpose of a precise separation between the products. Thus, an efficient conveying operation, for example with the aid of an overlapping flow, is inherently not possible or is possible only under difficult conditions.
It is correct per se that the conveying of individual sheets has a tendency to lead to high cycle rates and consequently also to high transport speeds. However, it must be taken into consideration that in particular the goal of achieving a high speed makes it necessary to insert gaps between the signatures into which the separating sword can dip, as is disclosed in the above mentioned EP1 334 938 A1.
In addition, it is recognized that the high conveying speeds of the signatures in the movement direction must ultimately be stopped abruptly by a front end stop for the further processing, wherein this regularly results in damage to the signatures. Problems with quality are thus encountered during the further processing of the signatures to finished products since this damage takes the form of tears and compressions, especially in the spinal region, thereby causing a noticeable increase in the associated ejection rate.